I would group this slightly differently.
There are "citizens" and there are "natural born citizens."
Because of the placement in Article II Section 1 ("No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President;"), "natural born citizens" are of two kinds: "natural natural born citizens" and "grandfathered natural born citizens." This is because the grandfather clause is in relation to eligibility to be president, not eligibility to be a citizen. Citizenship was declared via the Declaration of Independence to all residents of the colonies at the time of the declaration.
So now there are three groups of citizens: "natural born citizens" (the posterity of We the People), there are "citizens" (people born here with non-citizen parents - not We the People), and "naturalized citizens" (people who were born elsewhere and became citizens.
"Citizens" can be Representatives and Senators, but not President. Only "natural born Citizens" can be President, because only this group "secures the Blessings of Liberty to ourselves and our posterity."
-PJ
The Constitution only mentions the possibility of three types of U.S. citizens - natural born, naturalized and those who were citizens at the time of the adoption.
Those who were ‘grandfathered’; i.e. citizens at the time of the adoption - were mostly natural born subjects of England - they were not, nor did they consider themselves, natural born citizens of the USA.
If they did they would have said “natural born citizens, including those who were citizens at the time of the adoption of the Constitution”. They did not (one type - OR- another type; not one type INCLUDING those grandfathered in).
The clear language of the Constitution says that two DIFFERENT types of citizens are eligible for the Presidency - natural born citizens and those who were citizens at the time of the adoption of the Constitution.
If there are only “citizens” and “natural born citizens” then are you claiming that a “natural born citizen” cannot be a Senator?
The language of the Constitution says a Senator must be a “citizen”. If “citizen” is its own category, separate from “natural born citizen” - then the clear implication would be that a “natural born citizen” wouldn’t be eligible for the office.
Now that right there is funny.